The present invention relates generally to internal combustion engine construction and more particularly to a crankshaft counterbalancing and lubricating system for an internal combustion engine.
The art of counterbalancing the effect of reciprocating masses in internal combustion engines is quite well established and such counterbalancing is frequently accomplished by providing one or more counterweights eccentrically positioned on the engine crankshaft opposite the eccentric location of the connecting rod crankshaft bearing. In this manner, the reciprocating mass typically including the piston and connecting rod is moving in one direction while the counterweight is moving in the opposite direction so as to tend to cancel out the inertial effects of piston reciprocation. While it is recognized that angular momentum or other imbalance problems remain, these are much less significant than the problems created by the linear motion of the piston and though those problems remain the engine is said to be balanced.
In some engine configurations there is insufficient internal clearance for the moving components to allow the presence of a crankshaft counterweight of sufficient size and location to balance out the reciprocating momentum of the piston to the degree desired by the designer, and in these situations it is known to supplement the effect of the counterweight by removing material from the crankshaft on the side of the crankshaft axis of rotation opposite the counterweight. Thus removing material from one side of the crankshaft has essentially the same effect as adding material to the opposite side of the cranksaft.
Schemes for lubricating bearings and other moving parts within an internal combustion engine are also quite well established. Two stroke cycle engines typically rely on a lubricant being mixed with the fuel and circulated therewith throughout the engine crankcase. Four stroke cycle engines typically employ an engine sump within the crankcase providing a lubricant source and that lubricant, such as common engine oil, may be distributed by splashing around during engine operation. For example, it is fairly commonplace to employ an oil dipper on the lower end of an engine connecting rod so that as the crankshaft rotates the connecting rod periodically dips into the oil in the engine sump, scooping up a dip of that oil for lubricating the crankshaft connecting rod bearing. Other engines may employ a so-called pressure lubricating system wherein an oil pump withdraws lubricant from the sump and distributes that lubricant through a network of lubricant flow paths to the various parts of the engine. For example, in one vertical crankshaft, single cylinder, four stroke cycle engine manufactured by the applicant's assignee, an oil pump is cam shaft actuated to pump oil upwardly through a drilled cam shaft passage to near the top of the engine and then that oil flows laterally into an upper main bearing oil groove for lubricating the upper main crankshaft bearing. That crankshaft also includes a drilled crankshaft passage extending from the main bearing oil groove downwardly to the crankshaft connecting rod journal for lubricating the connecting rod bearing. As the oil leaks away from the connecting rod bearing, it is slung outwardly by centrifugal force in a generally horizontal plane so as to lubricate the piston, wrist pin, cylinder side walls and other components of the engine.
Unfortunately the crankshaft oil passageway of the last mentioned lubricating scheme passes directly through the region which would be cored or removed if one were to attempt the earlier mentioned counterbalancing scheme employing a combination of counterweights and voids. Prior attempts to wed this lubricating scheme and cored counterbalancing scheme have necessitated the relocation of the lubrication passageways in the crankshaft to prevent the counterbalance hole from interrupting the oil passageway. Such relocation is costly in that circuitous lubricating paths must be formed in the crankshaft and is also costly in the sense that the same crankshaft configuration cannot be employed in both counterbored and coreless balancing environments. It would be highly desirable to provide a crankshaft configuration having the advantages of the cored counterbalancing configuration while retaining the advantages of the simplistic linear crankshaft lubricant passageway which extends from the main bearing oil groove obliquely to the crankshaft axis and directly to the crankshaft connecting rod journal.